Railway traffic controlling apparatus



April 5, 1938- B. YARBROUGH RAILWAY TRAFFIC CONTROLLING APPARATUS As sheds-sheet 1 Filed March 5;' 1956 y HIT m M llll i@ @JHT m m T Q W mw m fl v T my m N Y m w u @NM ww mm www Nm@ A m QM@ @Wld y wm T w l. NN NK. D WQ 1w" Sw ww Q GLUT m .w @KES w n n www WL @5%. 1 l .m n NW wm April 5, 1938 B. YABROUGH RAILWAY TRAFFIC CONTROLLNG' APPARATUS a'sheets-sheet 2 N MVLI MQ" ,ma NNN R NNN EN IB.

,EN N ,NNN N www U mmv n ND BY@ HIS ATTORNEY -April 5, 1938. l.; B. YARBROUGH RAILWAY TRAFFIC CONTROLLING APPARATUS Filed March 3, 1936 UN .m

INVENTOR 3 Sheets-Sheet 3 awr ATTORNEY Patented Apr. 5, 1938 UNITED STATES PATENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Application March 3,

11 Claims.k

My invention relates to railway traino controlling apparatus, and particularly to signaling apparatus for governing the movement of traffic over stretches of single track over which traiiic 5 moves in both directions.

I will describe two forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1A, 1B and 1C, when placed end to end in order with Fig. 1A at the left, constitute a diagrammatic View showing apparatus embodying one form of my invention applied to that portion of a single track railroad located between and including the ends of two adjacent passing sidings, while Figs.

1A and 1C placed end to end in the reverse order, that is, with Fig. 1A at the right of Fig.

1C, form a diagrammatic view showing the apparatus of my invention applied to the double track 90 portion oi the railroad which includes the siding situated between two adjacent single track stretches. Fig. 2 illustrates a modification of a portion of the apparatus of Fig. 1B., having to do with the approach lighting of the signals and also embodying my invention.

One object of my invention is the provision of a novel absolute-permissive block signaling system, in which the signals for both directions are controlled over circuits employing but twoline wires, and in which the relative polarity of the current supplied to the line circuit at one end or the other may be reversed to provide three-position control of the signals for both directions. A feature of my invention is the provision, in a system of this character, of means for preventing short circuits when two current sources are connected to the opposite ends of the same line circuit in such direction that their effects are additive.

Another object of my invention is the provision of an improved system of directional control for the single track stretch, which operates upon the approach of a train towards a signal that has been cleared, to maintain the established traffic direction until the train vacates the stretch.

A further ob-ject of my invention is the provision of improved means for lighting the signals upon the approach of a train, which operates in such a manner as to render the signal visible when the train is at a greater distance than heretofore without the use of additional line wires.

Other objects and purposes of my invention will be made apparent as the description pro- 55. ceeds.

1936, Serial No. 66,811

In order to simplify the drawings and to enable the circuits to be more readily traced, I have herein identified each switch and signal by a number and each relay by a letter or combination of letters with a distinguishing prefix identifying the switch or signal with which the relay is associated. The various relay contacts are identitled by numbers and those contacts not adjacent the respective relays which operate them bear the reference characters 4for the respective relays as well as the numbers identifying the contacts. Furthermore, instead of showing the sources of current for energizing the various line and local circuits Vand the wires leading thereto in detail, I have shown only the terminals` of the sources, which I have designated by the reference characters B and C, referring to the power supply and common return terminals, respectively. It is to be understood that in acccrdance with the usual practice, a separate local source of current is provided at each location, for each direction.

Referring to the drawings, the references I and la designate the track rails of the main track of a single track railway over which traffic may move in either direction, the track rails being divided into sections by insulated joints 2, each section being provided with a track circuit identified by the reference character T with a distinguishing prefix. Each track circuit is provided with the usual track battery 3 and with a track relay identified by the reference TR with a prex corresponding to that of the associated track circuit. Power-operated track switches 5 and 'I connect the two ends of a non-track circuited passing siding PS with the main track, and the movement of trailic over these switches is governed by signals bearing the references 6 and 8, respectively, each signal being identiied by a distinguishing prei-lx. The head block signals RAB and RCS govern trafc moving from left to right on the main track or from the siding, respectively, over switch 5 into the adjacent single track stretch, and considering the drawings IA, IB and IC to be arranged end-to-end in that order, it is to be noted that the control limit of these signals, as far as opposing traffic is concerned, extends to the opposing head block signals LAS andLCS which are similarly arranged to govern traic moving from right to left over 50 the same territory. The spacing of trains moving in the same direction through the single track stretch is governed by the intermediate signals I2 and I0, or by signals II and I3, of Fig. 55

1B, depending upon the direction of movement, as will be apparent from the drawings.

Considering now that Fig. 1A is placed to the right of Fig. 1C so as to further extend the territory illustrated it will be noted that signal RA8 governs tramo moving from left to right on the main track of the double track portion, and that its control limit, as far as opposing traic is concerned, extends to the corresponding opposing signal LA when switch 5 is normal, but only to signal RAt` which is then at stop, when switch 5 is reversed to permit an opposing train to enter the siding. The circuits are symmetrically arranged with respect to the two directions, and the control limit of signal LAS similarly extends to signal RA8 when switch l is normal and to signal LAB, then at stop, when switch 'l is reversed. Signals RBB and LBS are slow speed signals governing the movement of traic into the siding, and their control limits extend only to the ends of the corresponding switch section.

It is to be understood that each of the track switches and the associated group of signals of Figs. 1A and 1C are subject to manual control from a remote point, such as a dispatchers ofce, through the medium of a centralized trafc control system. To illustrate such control in its relation to the present invention, considering Fig. 1A for example, (that shown in Fig. 1C being similar) a dotted line connection is shown extending from a switch machine 5W for controlling switch 5 to a two-position switch lever SW and also to two switch indication relays ENWP and ERWP, and it is to be understood that in accordance with the usual practice that when lever SW occupies position N, as shown, switch 5 is operated to normal, relay SNW'P is energized and relay SRWP deenergized, as shown, but that when lever SW occupies position R, switch 5 is reversed, relay ERVVP is energized and relay SNWP deenergized. The manual control of the signals is effected by energizing one or the other of a pair of signal control relays which are identied by the reference HS with distinguishing prex, such, for example, as the relays REI-IS and LSHS of Fig. 1A, and as illustrative of the manual control of the signals, dotted line connec` tions are shown from these relays to a three-position signal lever bearing the legend Sig and a reference number. It is to be understood that when lever 5, for example, is in its mid-position as shown, the signals identified by the same number are at stop, but when the lever occupies position L or R, relay LBHS or REHS will be energized to clear one of the associated signals 6, subject to control by traffic conditions and in accordance with the position of the track switch and the condition of the opposing signals, to permit a traic movement toward the left or right, respectively, over the associated track switch.

Each of the signals is illustrated as of the searchlight type, such for example as that disclosed in the Reissue Patent No. 14,940, granted to Eli J. Blake on August 31, 1920. Each signal mechanism bears the reference M with a prex similar to the designation of the corresponding signal, and each mechanism including a three-position circuit controller. It is to be understood that when the Winding of a signal mechanism is energized by current of one relative polarity, front contact G and back contact Y of its circuit controller are closed, as illustrated for example by mechanism HM, as shown, and the signal then displays a green light indicating clear or proceed; that when the winding is energized by current of the opposite relative polarity, front contact Y and back Contact G of the circuit controller are closed, as illustrated for example by mechanism ISM, as shown, and the signal then displays a yellow light indicating caution; and that when the winding is deenergized both back contacts are closed, as illustrated by the remaining mechanisms, as shown, and the signal then displays a red light, indicating stop. Each signal is electrically lighted by a lamp E which is energized continuously in the case of the manually controlled signals, while the intermediate signals are lighted only upon the approach of a train, as will be hereinafter explained.

Each signal mechanism controls a repeating relay bearing the reference H with a prefix identifying the corresponding signal, which relay is energized when the signal indicates proceed or caution and serves to control the energization of the next signal in the rear for the same direction. Each relay H associated with a head-block signal is of the slow-release type, While each relay H associated with an intermediate signal is a slow pickup slow release relay, as indicated conventionally on the drawings by transverse arrows applied to the contacts of these relays. A directional stick relay designated by the reference S with identifying prex, is associated with each relay H controlled by the intermediate signals of Fig. 1B. These relays serve to provide the so- Called absolute-permissive feature of the scheme of control, and operate in such a manner that when a train enters the single track stretch all signals for the opposing direction are held at stop until the entire stretch is vacated, While the signals for the same direction are caused to successively indicate caution and proceed in the rear of a moving train so as to permit following trains to enter the single track stretch and to properly space the movement of these trains through the stretch.

It is to be understood that switch locking means, not shown in detail, is provided to prevent operation of the track switches except when conditions are proper. The switch locking means includes a pair of approach locking stick relays, one for each direction for each switch, which relays are identied in the drawings by the general reference LS. Considering the approach locking stick relay RSLS, for example, (the scheme of control for the remaining relays LS being similar), it is to be understood that switch machine 5W is locked against operation unless relay RSLS is energized, that relay RGLS is energized only when a signal indication relay R6RP is energized, and that the latter relay is energized only when the home signals RCS and RAB for the corresponding direction indicate stop and the distant signal, which is signal RA8 in this instance, indicates stop or caution. Furthermore, if signal RCS or RA6 is put to stop manually, the energization of relay RBLS may be delayed for a time interval following the energization of relay RERP by the operation of a time element relay STE, Which relay is checked to insure that it occupies its normal position when the signals are put to stop by including a back Contact thereof in the signal control circuits. This control of the approach locking relays LS by the signal indication relays RP is indicated by a dotted line connection between these relays, and may be arranged as disclosed in Fig. 2 of Patent No. 1,952,072, granted May 15, 1934, to H. A. Wallace, for Railway traffic controlling apparatus. A1- though the switch locking forms no part of the present invention, the approach locking relays are shown herein because front contacts of the relays LS for each direction are included in the control circuits for the signals for the opposite direction, as will be pointed out hereinafter, and these relays not only control the switch but also serve to prevent clearing of two opposing signals at the same time and safeguard the reversal of traffic if a signal is put to stop in the face of an approaching train.

` Since the relative polarity oi the current supplied to the line circuits for the contro-1 of the signals is reversible, and since the same line wires are used for the control of the signals for both directions, it may happen that current sources may be connected at opposite ends of the same line wires in such direction that their effects are additive. To -prevent excessiveiow of current under this condition, I include a series relay identified by the general reference Z in each line circuit where this may occur. Each relay Z is adjusted to be non-responsive to the normal line current due to the voltage of a single source and to pick up only under the double voltage condi'- tion mentioned, in which case the relay will open its back contact to include a resistor I 4l in the line circuit so as to reduce the current to a safe Value, but not enough to release the relay Z as long as it is energized by the two sources in series.

As illustrated in the drawings, the apparatus is shown in the condition which it assumes following a train movement from right to left', all ofthe head block signals being at stop. The intermediate signals are not lighted, although mechanism I3M is energized in the caution position and mechanism IIM in the clear position. The relays which repeat the stop indication of the A signals, such as relay RAGRP, are energized. The circuits for all such relays shown are similar, and that for the one referred to may be traced from terminal B, back contacts G and Y of the circuit controller of mechanism RASM,

relay RABRP to terminal C. The signal indica-- tion relays such as RGRP are also energized. The circuit for RSRP, for example, may be traced from terminal B, back contact G of the circuit controller for signal RAS, wire I5, fro-nt contact I6 of relay RABRP, back contacts G and Y of the circuit controller for signal RCS, relay RBRP to terminal C. Relay RSRP being energized, the approach locking relay RBLS is likewise energized, as indicated on the drawings, and each of the remaining relays LS are also energized. The winding of the mechanism for signal I3 is energized over a circuit which may be traced from terminal B, back contact I1 and winding of relay I 3Z, back contact I8 of relay LABI-I, front contact I9 of relay RBLS, back contact 20 of relay RIBHS, front contacts 2l and 22 of track relays 5TR and 4TR, line wire 23, front contact 24 of track'relay I3TR, back contacts 25 and 26 of relays 12H and I2S, winding of mechanism I3M, back contacts 21 and 28 of relays I 2S and I 2H, front contact 29 of relay I3TR, line wire 36, contacts 3| and 32 of relays 4TR and 5TR, backI contact 33 of relay RBHS, front contact 34 of relay RSLS, back contact 35 of relay LABH, to terminal C. Mechanism ISM is energized in the caution direction over the circuit just traced, but relay I3Z remains in itsv deenergized position. Relay I3H is now energized over a circuit which may be traced from terminal B, back contact G and front contact Y of mechanism I3M, front contact 36 of relay I2TR, relay I3H to terminal C. The energization of relay-I3H completes .af circuit which may be traced from terminal B, back contacts G and Y of I2M, front `contact 31 of relay I3H, contact 38 of track relay IZTR, line wire 39, contact 40 of track relay IITR., back contacts 4I and 42 of-relays VIIlI-I and IIIS, winding of mechanism lIM,contacts y43, 44, 45, line wire 46, contacts 41 and 48 to terminalC. Mechanism I IM is energized in the clear direction over this circuit. f

Assuming now with the apparatus as shown that the operator desires to effect a train movement from section 6T through the `singletrack stretch from left to right, and that signall lever=6 is moved Ato Aposition R to energize relay-RGHS, lever SW vfor switch 1 being in position N. The energization of relay RGHS opens back contacts 20 and 33 in the circuit for I3M, thereby causing this mechanism to assume the stop position, .deenergizing relay I3H. When relay kI3H releases it opens contacts 31 and 48 in the circuit for I IM, which assumes the stop position,deenergizing relay IIH.` When relay IIH releases it completes a circuit for IUM which may be traced from terminal B, back contact 49 and winding of relay IZ, back contact 50 of relay RA8H,'front contact 5I of relay LBLS, back contact 520i `relay L8HS, front contacts '53 and 54 of relays-.1TR and STR, line wire 55, front contact 5610i relay IUTR, 'back contacts 51 and 58 of relays IIH and I IS, winding of IOM, contacts 59, 60, 6I,line Wire 62, contacts 63, 64, 65, 66, 61 to terminal yC. Mechanism vIIIM is now energized in the caution direction, completing a circuit for relay I 0H similar to that already traced for relay I3H, and relay IIIH When energized completes `a circuit `for I2M which may betraced from terminal B, back contacts G and Y of IIM, front contacts 4I and 43 of relays IGH and II'I'R, line wire 39, front contact 38 of relay 'I2TR, back contacts 31 and 68 of relays I3H and I 3S, winding of relay I2M, contacts 69, 48, 41, line wire 46, front conta-cts `45 and 44 to terminal C. Mechanism I2M is now energized in the proceed direction, completing thecircuit for relay I2H, and relay 12H when energized completes a circuit for RABM,A which may be traced from terminal B, back contacts G and Y of mechanism I3M, front contacts 25 and 24 of relays I2l-I andl I3TR, line Wire 23, front contacts 22, 2|, 20 and 10 of relays 4TR, 5TR, RBHS and ILRP, back contact 1I of relay LBHS, front contact12 of relay 5TR, back contact 13 of relay ETE, front contacts 14 and 15 of relays RBHS and 5NWP, win'ding of relay RASM, front contacts 16, 33, 32, 3I, line Wire 30, front contacts 29 and 28 to terminal C. Signal RAG nowindicates proeed, relay RABH becomes energized and relay RAGRP` is deenergzed. The release o f the latter relay causes relays RBRP and RSRS to release in sequence, and relay RBRS when released locks switch 5 and also opens contact 1'1 in the circuits for controlling signals LA6 and LBS vand contacts I9 and 34 in the circuit for controlling signal I3.

Assuming next with the apparatus as shown that the operator desiresto effect a train movement from siding PS through the single track stretch from left to right, and that signal lever 6 is moved to position R after switch '5 has'been reversed in response to a movement of lever SW to position R. The several operations which result from the energization of relay RSHS 'now take place as already described in connection with the clearing of signal RAB, except that since relay 5NWP is now deenergized, mechanism RA6M is disconnected from front contacts 14 and 33 of relay RBHS. However, relay 5RWP is now energized and connects these contacts to mechanism RCSM over front contacts 18 and 19, so that RCSM is energized in place of RABM. It will be apparent from the drawings that the circuit for controlling signal RCS is otherwise identical with that for signal RAG, and that mechanism RCGM when energized likewise releases relays RGRP and RSLS to lock switch 5 and the opposing signals. It follows, therefore, that signal RAS or RCS, dependent upon the position of switch 5, can be cleared only when all opposing signals up to and including signals LAS and LC8 are at stop, and all track sections between signal RAB and RA8 at stop are unoccupied.

I will now assume that a train moving from left to right accepts signal RAG or RC6 and passes through the single track stretch. When the train enters section 5T, track relay 5TR releases to open contacts 12, 2| and 32 in the signal control circuit to put the signal to stop. It is to be understood that relay REHS also releases and that the operator restores lever 6 to normal. Signals RAG and RCS will therefore remain at stop until lever 6 is again operated. As the train proceeds, track relays 4TR and I3TR release successively, the apparatus of Fig. 1A again assuming the condition shown as soon as the train vacates sections 5T and 4T. When the train enters section |3T, the'release of track relay ISTR completes the lighting circuit for signal I2 which extends from terminal B, back contact of relay I3TR, lamp |2E, back contact 86 of relay |3S to terminal C. Mechanism I2M being energized in the proceed position, the lighting of lamp I2E causes signal I2 to display a proceed indication to the approaching train.

, At the same time, contact 8| oi relay I3TR drops to open the circuit for relay 12H and to complete a circuit for the directional stick relay I2S, which may be traced from terminal B, front contact G of mechanism I 2M, back contact 8| of relay ISTR, front contact 82 of relay IZI-I, back contacts 83 and 84 of relays IBS and ISH, relay I2S to terminal C, whereupon relay I2S picks up, completing a temporary stick circuit from terminal B, front contact G of I2M, back contact 8| of relay I3TR, front contact 85 and winding of relay I2S to terminal C. As hereinbefore mentioned, relay I2H is a slow pickup, slow-release relay, and when it releases a second stick circuit for relay I2S is closed which extends from ter minal B, back contact 82 of relay |2H, front contact 85 and winding of relay I2S to terminal C. It follows, therefore, that relay I2S remains picked up as long as relay I2H remains deenergized, that is, as long as section |3T is occupied or signal I2 remains at stop. v c

It is to be noted that the pickup circuit for relay I2S includes back contacts 83 and 84 of the corresponding relays I3S and I3H for the opposite direction and that the circuit for relay I3S is similar to that for relay I2S and includes back contacts 81 and 88 of relays I2S and 12H. The two relays I2S and ISS are therefore fully checked so that but one direction of traiTic can be set up at a time.

One purpose of the directional stick relays S is to provide directional control of the approach lighting circuits for the intermediate signals. Thus lamp |2E is lighted when a train approaching signal I2 enters section |3T, as already described, but not when a train moving in the opposite direction enters section |3T, because then re, lay I3S will be energized and Will open the circuit.

for lamp I2E at its back contact 86. Another purpose of the directional stick relays S is to supply current of reverse polarity to the line circuit for the next signal in the rear. Thus when relay I2H releases closing back contacts 25 and 28, front contacts 26 and 21 of relay I2S supply current of reverse polarity to line wires 23 and 30 included in the control circuit for signals RAG and RCS, as soon as the train vacates section I3T and relay ISTR picks up. However, in the case described it has been assumed that relay RSHS has been released, and it follows that this line circuit now includes a current source at each end and that these sources are connected in the additive direction. This circuit may be traced from terminal B of the source adjacent signal I3, back contacts G and Y of ISM, front contact 21 of relay I2S, thence as already described over line wire 30, to back contact 35 of relay LABH, terminal C of the source adjacent signal LAG, through this course to its terminal B, back contact I1 and winding of relay |3A, back contact I8 of relay LAGH, thence over line wire 23, front contact 26 of relay I2S to terminal C of the first-mentioned source. Relay I3Z picks up under this condition and by opening back contact I1 inserts a current limiting device as illustrated by the resistor I4 in the line circuit so as to prevent an excessive flow' of current. This overload condition exists only when relay IS is energized, but when relay |2H is energized to supply current of normal polarity to the line. circuit the sources at the two ends are in opposition so that substantially no current will flow and relay I3Z is not operated.

If, now, with relay I2S energized, the operator reenergizes relay RBHS to permit a following train to enter the stretch, the control circuit for signal RAS or RCE as already described will be reestablished, except that in this case the polarity will be reversed. It follows that signal RAG or RCS will indicate caution if relay RBHS is operated when a train moving from left to right has vacated section I3T and signal I2 is at stop.

Assuming now that the train continues through section I2T and enters IIT, the release of IITR will complete a circuit for lamp HIE causing signal I0 to display a caution indication to the approaching train, because, as already pointed out, IDM is energized in the caution direction, and relay IOS will be picked up and relay IDH released in a manner similar to that described for the corresponding relays associated with signal I2. It follows that mechanism |2M will become energized in the relay I ITR to pick up. When I 2M becomes energized, relay I2H again picks up, breaking the stick circuit for relay I2S so that relay I2S releases. Current of normal polarity is now supplied over front contacts 25 and 28 of relay I2H to energize RAB or RBB in the clear direction, so that signal RAB or RBB will also indicate proceed, providing relay RBI-IS is energized.

` I will next assume that the operator reverses switch 1 and moves lever 8 to the right to energize relay RSI-IS, in order to route the train moving from left to right in the single track stretch into the siding at the right of section 1T. With switch 1 reversed, it is to be understood that relay 1NWP is released and 1RWP is energized. With relay R8HS energized the circuit for RBBM is closed, and may be traced from terminal B, front contact 89 of relay 1RWP, back contact 90 of relay 1N`WP, front contact 9| of relay LSLS, back contact 92 of relay LSI-IS, front contact 93 of relay 1TR, back contact 94 of relay 1TE, front contacts 95 and 96 of relays R8HS and 1RWP, winding of RBSM to terminal C. When RB8M is energized, signal RBB indicates caution, or slow speed, and relays R8RP and RBLS are released to lock switch 1 and the opposing signals. The distant signal I0 remains at caution when signal RBB is energized.

Considering for the moment that the operator had energized relay RSHS with switch 1 normal to clear signal RAS, relay RASH will become energized and its contacts and B1 will reverse the polarity of the current supplied to IBM. It follows that signal I0 will display a proceed indication to an approaching train only in the event switch 1 is normal and signal RAB indicates caution or clear.

Assuming now that the train moving from left to right passes signal RBB or RAS, when the train enters 1T7 track relay 1TB, releases to open contact 93 to restore the signal to stop. When the train vacates section 9T, mechanism |0M will become energized in the caution direction, because relay RARI-I is deenergized, energizing relay IGH' and releasing relay IOS, and current of normal polarity will be supplied to line wires 39 and 46 to energize mechanism |2M in the proceed direction. The apparatus of Fig. 1B will then be in a condition similar to that shown except that the direction of energization of the line circuits is reversed. Thus considering the block comprising the track sections IIT and I2T, the right-hand leaving signal I0 is energized in the caution direction in place of the similar left-hand signal I3, as shown, and the entering signal I2 is energized in the proceed direction in place of the similar signal I, as shown.

I will next assume that with Figs. lA and 1B placed at the right of Fig. 1C to further extend the territory illustrated, and with switch 1 reversed to permit trains moving from left to right to enter siding PS, that the operator moves lever 6 to position L with switch 5 normal, to energize relay LSI-IS to permit a train` moving from right to left to pass on the main track. The train or trains on the siding obviously will be held there by signal RCB until the opposing train vacates section 5T and switch 5 is restored to normal, the circuits for controlling signal RCG already having been described in detail. Signal LAB is at stop because switch 1 is reversed, and when the operator energizes relay LSI-IS a circuit for energizing LASM is closed which may be traced from. terminal B, back contact 91 of relay LABH, front contacts 98 and 99 of relays 1RWP and BTR, line wire |00, front contacts ISI, |02, |03, and |04 of relays ETR, LSI-IS, SNWP and 5TR, winding of LASM, front contacts E05, 1| and 12 of relays SNWP, LGI-IS and ETR, back contacts 13 and 14 of relays ETE and RSI-IS, front contacts 11, |06, |01 and |08 of relays RSLS, 5NWP, LBHS and GTR, line wire |09, front contacts Ill! and I|| oi relays 8TR and 1RWP, back contact I|2 of relay LASH to terminal C. Relay LABl-l being deenergized, signal LAB is energized to indicate caution, causing relay LAII-I to be energized to reverse the polarity of the current supplied to its distant signal I3 as already explained in connection with the similarly arranged signals RAS and I9 for the opposite direction.

After the trains moving toward the right into siding PS vacate section 1T, signal RB!) may be held at stop b-y restoring lever 8 to normal to release relay RSHS. Switch 1 may then be restored to normal, whereupon the operator may move signal lever 8 to position L to energize relay L8HS to clear signal LAS.

The circuits for controlling signal LAB are similar to those for the corresponding signal RAS already described, as is apparent from the drawings, and therefore these circuits will not be traced in detail. Since relay RSHS is released before the switch is operated, contact 98 of relay 1RWP in the circuit for clearing signal LAB becomes shunted by a branch circuit including back contact H3 of relay RBHS and contacts ||4 and ||5 of relays 'ITR and R8LS, while contact III o1 relay lRWP is shunted by a similar branch including contacts IIS, I I1 and H8, as soon as section 1T is vacated and the locking for switch 1 is released, so that the circuit for LASM is not interrupted when switch 1 is restored to normal and relay 1RWP thereby deenergized.

When signal LAS assumes the caution. or proceed position, relay LA8H becomes energized and its contacts 91 and ||2 reverse the polarity of the current supplied to LABM to cause the indication of signal LAB to change from caution to proceed.

Assume now that with relay LA8H energized, that the operator restoresl signal LAG to stop by releasing relay LSI-IS, the terminals B and C of the source adjacent signal LA8 Will then be connected to the left-hand ends of line wires |09 and |00, respectively, over front contacts I|2 and 91 of relay LAI-I, While the terminals C and B of the source adjacent signal RAB Will be connected V to the right-hand ends of these line wires in such a direction that the effects of the twosources are additive. Thus a connection will be made from terminal B of the source adjacent signal RAB over back contact ||9 and winding of relay R8Z, contacts |20, |2I, |22, |02 and |0I to line wire |00, and thence over front contact 91 to terminal C of the source adjacent signal LAS, through this source to its terminal B, and thence over front contact ||2 to line wire |09, and from line Wire |09 over contacts |08, |01, |23, |24 and |25 to terminal C of the first-'named source. Relay R8Z will therefore pick up, and by opening back contact ||9 will introduce a resisto-r I4 into the line circuit so as to prevent an excessive llow of current under this condition. It is evident that this condition exists only when relay LABH is energized, and that when this circuit is in the condition shown in the drawings the sources at the two ends are in opposition so that substantially no current will flow and relay R8Z not be' operated.

It is readily apparent from the drawings that in arranging a meet as hereinbefore described,

the operator could have as Well routed the trains moving from left to right over the main track and rout-ed the opposing train through the siding, since the circuits are symmetrically arranged for both directions. In such case the operator would have cleared the slow speed signal LBS over cirable to provide approach control of the lighting of the intermediate signals as hereinbefore described, in the interest of economy of current, but if the train speeds are high and their stopping distances are relatively great, or if the block sections are short it may be desirable to cause the signals to become lighted when the approaching train is at a greater distance than that provided by arrangement of Fig. 1B. In order to extend this distance, but without the use of additional line wires, I propose to modify the circuits of Fig. 1B by including the apparatus of Fig. 2 for controlling the connections of the track batteries to the track rails. It is to be understood that Fig. 2 may be substituted for the corresponding portion of the block including track sections I IT and I2T, and that similar arrangements may be provided for the other blocks. Referring to Fig. 2, a series relay IIA or IZA is included in the connection between the track rails and track battery 3 for the two adjacent sections I IT and IZT, and each relay IIA or IZA when energized operates a contact |26 or I2'I to disconnect the track battery 3 and to shunt the track circuit including the other relay.

'Ihe relays IIA and I2A are non-responsive to the current which operates the respective track relays III'RI and I2TRl but pick up due to the increased flow of current resulting from the shunting of the track relay by the wheels and axles of a train occupying the section. It follows that when a train moving from left to right passes signal I2, relay I2TR will be shunted and relay IZA will be operated, and contact I2'I will then disconnect battery 3 from and will short circuit the rails of section IIT to cause IITR to release also, so as to close its back contact |28 to light lamp IUE. Signal IU will therefore become lighted when the approaching train enters section I2T instead of when the train enters section IIT, thereby substantially doubling the distance available for stopping the train in the event the signal indicates stop.

It also follows that when relays A are used, relay IUS will become energized when the train approaching signal I0 enters section I2T rather than when it enters section I IT, but this is without significance, and the apparatus in its modied form as illustrated by Fig. 2 operates generally in the same manner as in the case of the form hereinbefore described in detail.

Although I have herein shown and described only two forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track comprising two adjoining track sections each having a track relay, said relays being situated at opposite ends of the stretch, signals at the ends of the stretch each distinctively operable in accordance with the polarity of the current supplied thereto for governing the movement of trac in opposite directions through the stretch, a reversible line circuit comprising two line wires extending from one end of the stretch to the other for controlling the signals, said circuit including front contacts of said track relays, switching means at each end of the stretch operable to connect either the adjacent signal or a source of current of a given relative polarity to the line circuit at that end, and means controlled by each said switching means in response to the deenergization of the track relay at the same end of the stretch for connecting a source of current of the reverse polarity to the line circuit at that end.

2. In a signaling system for railroads, a stretch of track comprising a block section over which traic moves in both directions, an entering signal and a leaving signal at each end of the stretch, a reversible line circuit comprising two line wires extending from one entering signal to the other for controlling said entering signals in accordance with traiic conditions in said stretch, means for each leaving signal for clearing such signal effective only if the adjacent entering signal is at stop, and means controlled by each leaving signal when cleared and by a train occupying the stretch and approaching said signal for energizing said line circuit at the end adjacent said leaving signal to cause the entering signal at the opposite end of the stretch to indicate caution when the stretch is vacated by said train.

3. In a signaling system for railroads, a stretch of track comprising a block section over which traiiic moves in both directions, an entering signal and a leaving signal at each end of the stretch, a reversible line circuit comprising two line Wires extending from one entering signal to the other for controlling said entering signals in accordance with traffic conditions in said stretch, means for each leaving signal for clearing such signal eiective only if the adjacent entering signal is at stop, means controlled by each leaving signal When cleared and by a train occupying the stretch and approaching said signal for energizing said line circuit by current of a given relative polarity at the end adjacent said leaving signal to cause the entering signal at the opposite end of the stretch to indicate caution when the stretch is vacated by said train, and means controlled by each leaving signal eiective if said signal is cleared when said stretch is unoccupied for energizing said line circuit by current of the opposite relative polarity to cause such entering signal to indicate proceed.

4. In combination, a stretch of railway track comprising a block section, signals at the ends of the stretch each distinctively operable in accordance with the polarity of the current supplied thereto for governing the movement of traflic in opposite directions through the stretch, a source of current at each end of the stretch, a reversible line circuit comprising twov line wires extending from one end of the stretch to the other for controlling the signals in accordance With traic conditions in the stretch, switching means at each end of the stretch independently operable to connect either the adjacent signal or source of current to said line circuit at that end, means at each end of the line circuit for reversing the polarity of the current supplied thereto, a relay connected in series with the source at one end which responds only when the source at the other end of the line circuit is connected thereto in the additive direction, and means controlled by said relay for reducing the flow of current in said line circuit when both of said sources are connected thereto.

5. In combination, a reversible line circuit cornprising two line wires, a source of current and an electroresponsive device selectively responsive to the polarity of the current supplied thereto at each end of said line circuit, switching means at each end of the line circuit independently operable to connect either the adjacent source or electroresponsive device to said line circuit at that end, means at each end of the line circuit for reversing the polarity of the current supplied thereto, a relay connected in series with the source at one end, and means controlled by said relay for limiting the ow of current when the two sources are connected to the line circuit in the additive direction.

6. In combination, a reversible line circuit comprising two line wires, a source of current and an electroresponsive device selectively responsive to the polarity of the current supplied thereto at each end of said line circuit, switching means at each end of the line circuit independently operable to connect either the adjacent source or electroresponsive device to said line circuit at that end, means at each end of the line circuit for reversing the polarity of the current supplied thereto, a current limiting device, a relay at one end of the line circuit which responds to the current in said line circuit only when the two sources are connected thereto in the additive direction, and means controlled by said relay when energized for including said current limiting device in said line circuit in series with the source adjacent said relay.

7. In a signaling system for railroads, a stretch of railway track over which traffic moves in both directions and comprising two adjoining track sections, a track relay for each section, one track relay being located at each end of the stretch, signals at the ends of the stretch for governing the movement of trac in opposite directions out of the stretch, a lighting circuit for each signal, means for closing each lighting circuit including a back contact oi' the track relay at the same end of the stretch, and means responsive to the shunting of the other track relay by a train at the remote end oi the stretch for releasing said rst named track relay.

8. In a signaling system for railroads, a stretch of railway track over which trafc moves in both directions, comprising two adjoining track sections, a track relay for each section, one being located at each end of the stretch, a source of current for each track section, an auxiliary relay in series with each said source, and means controlled by each said auxiliary relay in response to the occupancy of the corresponding track section for opening the track circuit for the other track sect-ion, a signal at each end of the stretch for governing the movement of traiic out of the stretch, a lighting circuit for each signal, and means including a back contact of each track relay for controlling the lighting circuit for the signal at that end of the stretch.

9. In combination, a stretch of track comprising two adjoining track sections, a track circuit for each section including a track relay connected across the track rails, one track relay being located at each end of the stretch, a source of current for each track section located at the junction of said sections, for energizing said track relays; two auxiliary relays, one being connected across the track rails of each section in series with the source of current for such section, and means controlled by each auxiliary relay in response to the occupancy of the corresponding track section by a train for releasing the track relay for the other section, comprising contacts of such auxiliary relay included in the connection to the track rails of the source of current for the other track section.

10. In a signaling system for railroads, a stretch of railway track comprising a block section over which traflic moves in both directions, electrically controlled entering and leaving signals at each end of the stretch, a reversible line circuit extending from one entering signal to the other and controlled by trafiic conditions in said stretch, a slow pickup slow release repeating relayv for each signal, means controlled in'accordance with traiic conditions for selectively energizing the leaving signal at one end of the stretch or the other, a circuit closed by eachsignal when energized for energizing the associated repeating relay, means effective when the repeating relay associated with a leaving'signal becomes energized to disconnect the adjacent entering signal from the line circuit and to then connect a source of current to the line circuit at that end to energize the entering signal at the other end over said line circuit, and means effective when the repeating relay for either entering signal becomes energized for preventing the energization of the adjacent leaving signal.

11. In a signaling system for railroads, a stretch of track comprising a block section over which trafc moves in both directions, electrically controlled entering and leaving signals at the ends of the stretch, each adapted to indicate stop, caution, or proceed, a reversible polarized line circuit extending from one entering signal to the other and controlled by traic conditions in said stretch, means for selectively energizing the leaving signal at one end of the stretch or the other to cause such signal to indicate caution or proceed, a slow pickup slow release repeating relay or each leaving signal, a circuit closed when a leaving signal indicates caution or proceed for energizing the associated repeating relay provided a portion at least of said block section is not occupied, means rendered effective when a repeating relay becomes energized to disconnect the adjacent entering signal from the line circuit and to then connect a source of current of a given relative polarity to the line circuit at that end t0 cause the entering signal at the other end of the stretch to indicate proceed, and direction selecting means rendered effective when a train governed by said signals vacates said stretch to supply current of the opposite relative polarity to said line circuit to cause said last named entering signal to indicate caution.

LOWELL B. YARBROUGH. 

